Using solid C2H6 and C2F6 as an example, the one-axis molecular rotation effect on thermal conductivity has been considered in orientationally-ordered (OO) and orientationally-disordered (OD) phases of simple molecular crystals. The influence of molecular rotation on the heat transfer processes has been studied by a modified method of reduced coordinates, which permitted separating phonon-phonon and phonon-rotation contributions to the total thermal resistance.